A spanglish term to describe a person who is acting like more than a “chach” (See term for “chach” wish i had a hyperlink here btw).
The “mu” acts as the spanish “prefix” for muchach. “Muy” means “very”. Similar to saying someone is very chach. More than a chach. They’re a muchach.
That guy over there, he ain’t nothin’, but a muchach.
muCHaaach.